The production of prescription eye glasses typically involves the grinding of lenses in accordance with the prescription and the coating of the lenses with one or more chemical coatings including, but not limited to, scratch resistant hard coatings and anti-reflective coatings. Once the coatings have been applied, the lenses can be cut to fit a specific frame shape.
Lens suppliers typically ship lenses with hard coatings. The grinding of lenses removes the hard coating from the ground surface(s) of the lenses. When applying coatings to the ground lenses, the best results are typically achieved by removing any remaining hard coating prior to the application of the new coatings. Although in some instances overcoating is sufficient or the lens does not include a hard coat, and stripping may not be necessary. Where stripping is required, the removal of the hard coat can be achieved by dipping the lenses into baths of chemicals that strip the hard coating from the lenses.
When stripping or coating lenses, dip line manufacturing equipment can be used to perform the dipping of lenses into the appropriate baths of chemicals. The lenses are typically mounted onto lens holders that attach to the dip line manufacturing equipment, which dips the lenses into the baths of chemicals. A typical lens holder is illustrated in FIGS. 1a and 1b. The lens holder 10 includes a body 12 including a clip 14, which is used to suspend the lens holder from a cross bar, and a leg 16 from which a stepped ledge 18 extends. A spring 20 is attached to the body 12 by a rivet 22. The spring includes two flexible arms that extend from the rivet to a pair of paddles 24. In order to more securely hold a lens, the stepped ledge 18 includes steps 26 that form a depression in the ledge in which the lens can rest. Similarly, the contacting surface 28 of each of the paddles is concave. The contacting surface is typically the edge of a piece of metal, which can be sharp and/or abrasive and scratch a lens. A lens mounted within the lens holder shown in FIGS. 1a and 1b is illustrated in FIG. 2. As can be seen from FIG. 2, the spring 20 flexes to accommodate the lens between the paddles 24 and the lens rests against the steps of the stepped ledge 18 and is cradled between the contacting surfaces 28 of the paddles.
When coating materials are distributed unevenly or show imperfections such as drips, bubbles, pits, etc. on a lens, which can occur due to a variety of reasons including a drip of coating material on the surface of the lens or a bubble of coating material forming between the lens and the lens holder and then bursting, the lens must be stripped of the coating material and recoated resulting in a delay in the completion of the prescription eye glasses. When a lens is scratched during the coating process, the lens is typically discarded and a replacement lens is ground resulting in a delay in delivery and an increase in cost.